U.S. Pat. No. 6,658,184, which is hereby incorporated by reference in its entirety, discloses an exemplary optical fiber module that includes a plurality of optical fibers surrounded by a flexible tube, which is referred to as a protective skin. The gaps between the optical fibers in the flexible tube are generally occupied by a hydrophobic gel. The gel not only forms a moisture barrier but also prevents damage to the optical fiber and its protective coating (e.g., upon gaining access to the optical fiber).
One drawback of using grease or other gel-like material is that, during the installation of such optical modules, the grease or gel-like material tends to emerge from the optical cables, necessitating additional cleaning operations. Moreover, it is unpleasant for personnel to come into contact with grease or other gel-like material during optical cable installations.
European Patent Application No. EP 0,296,836 (and its counterpart U.S. Pat. No. 4,976,519, which is hereby incorporated by reference in its entirety) relate to an optical fiber cable that includes an inner sheath containing at least one optical fiber member, and an outer sheath surrounding the inner sheath. An intermediate sheath may be provided between the inner and outer sheaths. The inner sheath completely surrounds and is in tightly packed, direct contact with the optical fibers.
U.S. Pat. No. 5,181,268, which is hereby incorporated by reference in its entirety, discloses a tight-buffered optical waveguide that includes a solid lubricant, which purportedly improves strippability.
U.S. Patent Application Publication No. US 2002/0168520, which is hereby incorporated by reference in its entirety, relates to an optical fiber whose core is surrounded by a cladding, which in turn is surrounded by one or more layers of coating material.
There is a need, however, for an improved, semi-tight (or loose) optical fiber unit that is free of conventional water-blocking greases or grease-like gels.